Abstract: Block Adaiski is located southeast of North Caspian Basin, where salt rock of mega-thickness developed in the late stage of Early Permian. Devonian-Permian covered under the salt rock belongs to pre-salt oil and gas bearing series, which is a set of marine facies formations mainly composed of limestone and clastic rock. Having been located in the sedimentary setting of Nan'en Depression, the facies formation features in rich source rocks, well-developed reservoir rocks, and favorable cap rocks, providing favorable geological conditions for pre-salt hydrocarbon accumulation. Research shows that pre-salt hydrocarbon reservoirs are the main components of the reservoirs in the area. Large traps are mainly distributed in pre-salt series. According to sedimentary settings and lithofacies palaeogeography as well as source-reservoir-cap rock combinations of hydrocarbon reservoirs, geological conditions for forming pre-salt oil and gas reservoirs in Block Adaiski are analyzed in detail, laying the foundation for further pre-salt exploration.

Key words: sedimentary facies, pre-salt oil and gas reservoir, trap appraisal, Block Adaiski, North Caspian Basin